This invention relates to an apparatus used with equipment for assembling a stack of alternating positive and negative plates which together form a cell for use in multi-celled lead acid storage batteries as generally employed for automotive, industrial and commercial applications.
The construction of a lead acid storage battery is generally accomplished by the series assembly of a plurality of discrete cells formed within a battery case, each cell having a nominal voltage, when charged, of about 2.0 volts. Each cell is constructed by combining a plurality of alternately arranged rectangular, relatively thin positive and negative plates to form a stack. As fabricated, each of the plates is in the form of a grid having a plurality of cavities filled with a "paste" of lead oxide and sufuric acid. Each plate also has an upstanding commoning lug and the plates are disposed so that all of the positive plate lugs lie along one side of the stack and all of the negative plate lugs lie along its opposite side. The stack is finished by inserting insulating separators between the plates to prevent the positive and negative plates from shorting out after the subsequent charging step and then casting a lead commoning strap onto the lugs.
In the production of battery plates, as in the production of most high-volume, massed produced items, there is a tolerance level within which the plates must be produced in order to be acceptable. However, within this tolerance, it is possible that there is a substantial variability both among the plates used within any given stack to form a cell and between the plurality of stacks which are assembled to form a battery. In the production of the battery, it would be highly advantageous if this variability could be accommodated and operated on in a single cycle of the production equipment used. This is especially critical at the processing stage where the positive lugs and the negative lugs within the cell have the lead commoning strap cast onto them prior to the placement of the inner-cell connectors which, when connected, act to form the series assembled battery.
One apparatus widely used for accomplishing the task of commoning the battery lugs within each stack is the Farmer Cast-On-Strap (COS) Machine. The Farmer Machine is adapted to produce, in a single cycle, a plurality of final assembled stack sufficient to make up one battery. The strap casting operation is done within the COS apparatus by holding the stacks with a rectangular, multi-celled device commonly referred to as a basket, while the straps are cast onto the lugs.
The basket itself is loaded on the COS Machine while being held on a fixture known as a basket loader. This is designed so that it fits more or less down the lengthwise centerline of each basket while leaving a pair of lengthwise spaces running one on either side of the underside of the basket so that the plate stacks may be inserted into a kit in either a lugs up or lugs down configuration, depending on the particular mode of operation within the COS Machine. The device provided with the Farmer Machine to do this is relatively simple and comprises basically nothing more than a long tang onto which the basket is slidably mounted and clamped during the loading operation. Where the plates are roughly the full width of the basket, there is no problem in using such a device since the sidewalls of the basket will align the plates with sufficient precision so that the positive and negative lugs are essentially lined up within the tolerance levels required for the strap casting operation. However, where the plates used are substantially narrower than the full width of the basket, it is quite possible either the plates or separators within each stack will be assembled so that they are not exactly lined up with each other or that the stack itself will be misaligned for the casting operation.
A second problem with these machines is the fragility of the lead sulfate paste. With any degree of rough handling, fragments of it will break free which, if not removed interfer with the close fit of the plates and separators within the basket prior to the casting.
With the fixturing available for the Farmer Machine, there is no easy way to correct these problems and it is usually necessary for the machine operator to manually push the separators and plates together so that they properly fit together and the lugs all line up within a given stack and then finally to make sure the stacks are all properly aligned within the basket space. From a production point of view, this is not a satisfactory situation since it slows down the operating speed of the system. Furthermore, since the Farmer Machine operates with a pot of molten lead nearby, the necessity for the operator to work so close to the machine creates a considerable safety hazard as well. It would be highly desirable if it were possible for the plate and stack alignment to be done automatically so that it would not be necessary for the operator to do anything more than simply insert the stack assemblies into the basket. The subject invention is adapted to accomplish this.